PHP

SSH Authenticate using a Smart Card Private Key

Demonstrates using a private key stored on an HSM (smart card or token) for SSH public-key authentication. A JSON template locates the private and public key objects by class, key type, and label, and the returned handles are bound to an SshKey object.

Background: PKCS#11 objects are found by attribute rather than by name alone, which is why a template describing the class, key type, and label is used. An important practical detail is that the returned handles are valid only for the lifetime of the PKCS#11 session — they cannot be cached and reused later, so a subsequent session must locate the objects again. Logging out and closing the session when finished releases the device for other applications.

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<?php

use Chilkat2\JsonObject;
use Chilkat2\Pkcs11;
use Chilkat2\Ssh;
use Chilkat2\SshKey;

// This example requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

// Demonstrates using a private key stored on an HSM (smart card or token) for SSH public-key
// authentication.  Public-key authentication means the client uses the private key, while the
// corresponding public key is installed on the server under the SSH account.
//
// Note: Chilkat's PKCS#11 implementation runs on Windows, Linux, macOS, and other supported
// operating systems.

$pkcs11 = new Pkcs11();

// Use the PKCS#11 driver (.dll, .so, or .dylib) for your particular HSM.
$pkcs11->SharedLibPath = 'C:/Program Files (x86)/Gemalto/IDGo 800 PKCS#11/IDPrimePKCS11.dll';

// The HSM PIN should come from a secure source rather than being hard-coded.
$pin = '0000';

// Normal user = 1
$userType = 1;

try {
    $pkcs11->QuickSession($userType, $pin);
} catch (\Chilkat2\Exception $e) {
    echo $e->getMessage(), "\n";
    exit;
}

// Provide a template describing the PKCS#11 object to find: an RSA private key labeled
// "MySshKey".  For how such a key is originally imported, see
// PKCS11 Import SSH Key
$jsonTemplate = new JsonObject();
$jsonTemplate->UpdateString('class', 'private_key');
$jsonTemplate->UpdateString('key_type', 'rsa');
$jsonTemplate->UpdateString('label', 'MySshKey');

$privKeyHandle = $pkcs11->FindObject($jsonTemplate);
if ($privKeyHandle == 0) {
    echo $pkcs11->LastErrorText, "\n";
    exit;
}

// The handle is only valid for the duration of this PKCS#11 session.  To use the key in a
// later session, find it again.
echo 'private key handle: ', $privKeyHandle, "\n";

// Find the corresponding public key by changing the class in the same template.
$jsonTemplate->UpdateString('class', 'public_key');

$pubKeyHandle = $pkcs11->FindObject($jsonTemplate);
if ($pubKeyHandle == 0) {
    echo $pkcs11->LastErrorText, "\n";
    exit;
}

echo 'public key handle: ', $pubKeyHandle, "\n";

// Create an empty SSH key object and tell it to use the PKCS#11 handles, indicating the key type.
$sshKey = new SshKey();
try {
    $sshKey->UsePkcs11($pkcs11, $privKeyHandle, $pubKeyHandle, 'rsa');

    $ssh = new Ssh();

    $port = 22;
    $ssh->Connect('ssh.example.com', $port);

    // Authentication uses the existing PKCS#11 session.  The signing happens on the smart card --
    // the private key never leaves the device.
    $ssh->AuthenticatePk('mySshLogin', $sshKey);
} catch (\Chilkat2\Exception $e) {
    echo $e->getMessage(), "\n";
    exit;
}

echo "Public-key authentication successful.\n";

// ... use the authenticated SSH session ...

$ssh->Disconnect();

$pkcs11->Logout();
$pkcs11->CloseSession();